Medical device lead assembly with variable pitch coil

ABSTRACT

A medical device lead assembly includes an end connector element having a plurality of fixed connection element tabs each respectively extending from the end connector element to a tab distal end, and a lead body having a plurality of lead filars extending through the lead body and forming a filar coil. Each of the plurality of lead filars is coupled to a corresponding fixed connection tab. Each of the plurality of lead filars have a diameter of less than 150 micrometers or less than 125 micrometers, or from 50 to 125 micrometers or from 50 to 100 micrometers. The filar coil having an outer diameter value being less than 1.5 mm and a first pitch within the lead body and a second pitch adjacent to the end connector element and the second pitch is greater than the first pitch.

BACKGROUND

Implantable electrical signal generators, such as pacemakers,defibrillators, neurostimulators, and the like, have been used to treata variety of diseases. Such devices generate electrical signals that aretransferred to a patient's tissue through electrodes present on a distalend portion of a lead. The proximal end portion of a lead, connected toa signal generator, typically contains a number of connectorscorresponding to the number of electrodes. Conductors, also referred toas wire filars or filars, run within and along the lead body andelectrically couple the connectors to the electrodes.

Fixing the filars that run within the lead body to an end connector isdifficult. As the dimensions and size of the implantable medical devicesdecrease, fixing filars to an end connector becomes even more difficult.Aligning a number of very small filars and joining these filars to thecorrect connection point on an end connector requires a high level ofskill and craftsmanship and takes time to join each filar to each endconnector connection point.

SUMMARY

The present disclosure relates to a medical device lead assembly with avariable coil pitch. In particular the coil pitch of the lead filarsincreases along a length of the lead body.

In one illustrative embodiment, a medical device lead assembly includesan end connector element having a plurality of fixed connection elementtabs each respectively extending from the end connector element to a tabdistal end. A lead body includes a plurality of lead filars extendingthrough the lead body and forming a filar coil. Each of the plurality oflead filars are coupled to a corresponding fixed connection tab. Each ofthe plurality of lead filars have a diameter of less than 150micrometers, or less than 125 micrometers, or from 50 to 125micrometers, or from 50 to 100 micrometers. The filar coil having anouter diameter value being less than 1.5 mm and a first pitch within thelead body and a second pitch adjacent to the end connector element andthe second pitch is greater than the first pitch.

In another illustrative embodiment, a medical device article includes astimulator, a lead contact having at least one stimulation electrode,and a lead body providing stimulation signal communication to thestimulation electrode. The lead body includes an end connector assembly.The end connector assembly includes an end connector element having aplurality of fixed connection element tabs extending from the endconnector element to a tab distal end. A lead body having a plurality oflead filars extending through the lead body and forming a filar coil.Each of the plurality of lead filars coupled to a corresponding fixedconnection tab. Each of the plurality of lead filars have a diameter ofless than 150 micrometers, or less than 100 micrometers, or from 10 to150 micrometers, or from 25 to 100 micrometers. The filar coil having anouter diameter value being less than 1.5 mm and a first pitch within thelead body and a second pitch adjacent to the end connector element andthe second pitch is greater than the first pitch.

These and various other features and advantages will be apparent from areading of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a general environmental viewfor a stimulation system embodiment.

FIG. 2 is a perspective view of the illustrative neurostimulation systemof FIG. 1.

FIG. 3 is a cut-away side schematic view of an illustrative connectionassembly with the guide hub.

FIG. 4 is a perspective diagram view of an illustrative guide hub.

FIG. 5 is a perspective diagram view of another illustrative guide hub.

FIG. 6 is a schematic diagram of an illustrative lead body filar coilhaving a variable pitch.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration several specific embodiments. It is to be understoodthat other embodiments are contemplated and may be made withoutdeparting from the scope or spirit of the present disclosure. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the properties sought tobe obtained by those skilled in the art utilizing the teachingsdisclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise.

As used in this specification and the appended claims, the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

As used herein, “have”, “having”, “include”, “including”, “comprise”,“comprising” or the like are used in their open ended sense, andgenerally mean “including, but not limited to”. It will be understoodthat “consisting essentially of”, “consisting of”, and the like aresubsumed in “comprising,” and the like.

The term “coupled” refers to two elements being attached to each othereither directly (in direct contact with each other) or indirectly(having one or more elements between and attaching the two elements).

The present disclosure relates to a medical device lead assembly with avariable coil pitch. In particular the coil pitch of the lead filarsincreases along a length of the lead body. The increased coil pitchimproves termination reliability of the lead filars onto an endconnector. The coil pitch may increase along the lead body toward theend connector. The coil is a multi-filar coil having at least 4, 8, 10or 12 filars and a coil outer diameter of less than 1.5 millimeter orless than 1 millimeter. The coil pitch can be increased along the lengthof the lead body by at least 1.5 times or at least 2 times. The leadfilars have a diameter of less than 150 micrometers, or less than 125micrometers. The variable coil pitch provides improved filar terminationwith the end connector and reliable weld joints even with filar trimlength variation. While the present disclosure is not so limited, anappreciation of various aspects of the disclosure will be gained througha discussion of the examples provided below.

FIG. 1 shows a general environmental view 10 for an implantablestimulation system. While a stimulation system is illustrated, it isunderstood that any implantable medical device having a lead body may beutilized with the variable pitch multi-filar coil and connectionassembly described herein.

Stimulation system 20 includes a stimulator 22 (such as aneurostimulator, for example), an optional stimulation lead extension30, and a stimulation lead 40. Stimulator 22 is typically implantedsubcutaneously in a patient's body 28 at a location selected by theclinician; although FIG. 1 illustrates stimulator 22 implanted in thepatient's abdomen, other locations are suitable. Stimulation lead 40 istypically fixed in place terminating near the desired location selectedby the clinician using a device such as an adjustable anchor.

FIG. 2 shows an enlarged view of implantable stimulation system 20having implantable stimulator 22, stimulation lead 40, and optional leadextension 30. Implantable stimulator 22 has a housing 24, a power supply(e.g., a battery) within housing 24, and stimulation electronics coupledto the power supply and coupled to a connector block 26, which is alsoknown as a terminal block. Stimulation lead 40 has a lead proximal end42, a lead distal end 44 and a lead body 45. At lead distal end 44 is anelectrode contact having at least one stimulation electrode (notillustrated). Lead extension 30 has an extension proximal end 32, anextension distal end 34, and an extension body 35. Lead proximal end 42connects to lead extension distal end 34 at connector 50; either or bothlead proximal end 42 or extension distal end 34 may include an electrodetip that engages with connector 50.

Lead 40 and lead extension 30 provide electrical communication fromstimulator 22 to the electrode contact at distal end 44. Lead distal end44 contains at least one electrode but in most embodiments has aplurality of such electrodes (e.g., 4, 8, 16, etc.). Extending throughlead 40 and lead extension 30 are electrically conducting wires, oftenreferred to as filars or wire filars, that couple stimulator 22 to theelectrode contact and its electrode(s). The filars form the variablepitch multi-filar coil extending along the lead body length.

The lead filars may, for example, be stranded (made up of many smallwires), braided-stranded or “BSW” (braided of many small wires), orsolid or monofilament. Extending over and covering the wire filars is anelectrically insulating jacket or sheath. Typically, this jacket is apolymeric material, such as ethylene tetrafluoroethylene (ETFE),polytetrafluoroethylene (PTFE), polyphenylsulfone, or soluble imide.Other materials that act as electrical insulators can be used. In someembodiments, a shielding layer or jacket may be present, optionally overthe insulating jacket. An example of one suitable shielding layer isdescribed in U.S. Patent Application Publication No. 2005/0222658.

This disclosure is directed to a variable pitch multi-filar coil andconnection assembly that may include a guide hub. The guide hub mayprovide filar management and filar alignment with the end connectorconnection tabs. This results in reliable intimate filar contact withthe end connector connection tabs and reliable weld joints even withfilar trim length variation and filars having a diameter of less than200 micrometers. This variable pitch multi-filar coil and connectionassembly can be utilized in any number of filar connection points in thelead 40 and/or lead extension 30 to provide electrical communicationfrom stimulator 22 to the electrode contact at distal end 44. It shouldbe understood that the following discussion of the modular end pieces orinterconnects of this invention makes reference to “lead”, “leads”,“lead body”, and the like, generically, and that this discussion is notlimiting to positions or uses of the end interconnects of thisdisclosure, but that they may be used at any location. It should also beunderstood that the end piece interconnector and the lead structurescould be used with applications other than just stimulators.

FIG. 3 is a cut-away side schematic view of an illustrative connectionassembly 100 with the guide hub 200. The medical device lead connectionassembly 100 includes a plurality of lead filars 120 in contact with acorresponding plurality of connection tabs 110 at a connection point112. The connection tab 110 forms a portion of the connection element105 such as an end connector. The lead body 125 includes 4 or more, or 8or more, or 10 or more, or 12 or more filars 120 in helical or spiralwound along the lead body 125 forming a variable pitch coil ormulti-filar coil, as described herein. Shielding 128 is illustratedpartially covering the spiral wound filars 120. Once positioned asillustrated, lasers can heat and melt a portion of the lead filar 120and/or the connection element 110 simultaneously to form the connectionfrom the filar to the connection element 110.

In many embodiments, each of the contacting filars flex against aconnection element so that one or both are in flexure, where one or bothdeflects within the elastic limit of each of the lead filars. The leadfilars extend the length of the lead body and are in electricalconnection with a lead contact at a distal end of the lead body, asdescribed above. In some embodiments, the contacting forms an anglebetween the lead filars in a range from 1 to 70 degrees, or from 25 to70 degrees, or from 30 to 50 degrees. The lead filars may have anyuseful size or diameter.

It has been found that the connection method is particularly useful whenthe lead filars 120 have a small diameter. In many of these embodimentsthe lead filar 120 has a diameter of less than 250 micrometers, or lessthan 200 micrometers, or less than 150 micrometers, or less than 125micrometers, or less than 100 micrometers, or from 50 to 150micrometers, or from 50 to 125 micrometers, or from 70 to 100micrometers. The lead filar 120 may be insulated and this insulation mayadd an additional 5 to 40 micrometers of thickness about the insulatedportion of the lead filar 120.

A weld joint is formed by heating and melting at least a portion of theend portion of each lead filar. The weld joint is initially metal in theliquid state. Surface tension holds the liquid metal in the weld pooluntil it cools to the solid metal weld joint. The guide hub allows for asingle presentation to the weld station and a simultaneous or sequentialweld of all of the plurality of lead filars to the connection elementtabs.

The melting step may form the weld without additional weld material. Inmany embodiments the weld is formed with a laser weld or an e-beam weld.This is particularly useful when the lead filars are formed of TiMo or aTiMo alloy. It has been found that β TiMo alloy increases in modulus andstrength when heated to the liquid phase (by transforming a portion toan a crystal structure). After the melting step, the weld is cooled tocomplete the connection.

The guide hub 200 may form an angle between the lead filar 120 and alongitudinal axis of the lead body 125 in a range from 1 to 70 degrees,or from 10 to 50 degrees, or from 25 to 50 degrees. The guide hub 200generally increases the pitch of the multi-filer coil as compared to thepitch of the multi-filar coil that is spaced further away from the guidehub 200.

FIG. 4 is a perspective diagram view of an illustrative guide hub 200.FIG. 5 is a perspective diagram view of another illustrative guide hub201. The guide hub 200, 201 extends from a proximal end 210 to a distalend 212 where the distal end 212 is disposed within the lead body (seeFIG. 3, 125) and the proximal end 210 is received within the connectiontabs (see FIG. 3, 110) of the end connector (see FIG. 3, 105). A lumen250 may extend through the hub 200, 201 extending from a proximal end210 to a distal end 212 to allow a stylet, for example to pass through.

Guide elements 221, 222 are circumferentially disposed about the guidehub 200, 201 to guide and provide filar management. In many embodimentsthe guide elements 221 are a plurality of co-extending spiral channels221. The lead filar 120 is disposed within the spiral channel 221.

In other embodiments, the guide elements 222 are a plurality of posts222 extending away from the outer surface of the tubular guide element201. The lead filar 120 is disposed between the plurality of posts 222.The posts 222 may be arranged along a longitudinal axis along a lengthof the tubular guide hub 201. The posts 222 may be arranged along alateral axis along a length of the tubular guide hub 201. In manyembodiments there are at least 8 or at least 10 or at least 12 posts222.

An alignment feature 230 may be disposed on the guide hub 200, 201 andbe configured to mate with the end connector (105) to provide rotationaland axial alignment of the filars (120). The guide hub 200, 201 mayprovide filar management and filar alignment with the end connectorconnection tabs (110). In some embodiments the guide hub 200, 201includes two alignment features 230.

In many embodiments, the alignment element 230 is a protrusion extendingfrom the tubular guide hub 200, 201 and is located between the proximalend 210 and the plurality of guide elements 221, 222. The alignmentelement 230 may be received between adjacent connection element tabs(110) as illustrated in FIG. 3.

The guide hub 200, 201 may assist in varying the coil pitch of the leadfilars 120. The guide hub 200, 201 may assist in increasing the coilpitch of the lead filars 120. Varying the coil pitch of a multi-filarcoil 120 is difficult, especially with small diameter lead filars 120 asdescribed herein. It is preferred that the lead filars 120 have a smallor tight coil pitch within the lead body to provide structural supportto the lead body. However, this tight coil pitch is difficult toterminate to an end connector element. Increasing the lead filar 120coil pitch assists in termination to an end connector element. The guidehub 200, 201 may assist in increasing the coil pitch of the lead filars120, as illustrated in FIG. 3.

The lead filars may form a greater coil pitch along the plurality ofguide elements than within the lead body. In many embodiments, the coilpitch along the guide elements is at least 1.5 times greater or at least2 times greater than the coil pitch within the lead body.

The guide hub 200, 201 may have an outer diameter of less than 1.5millimeter or less than 1 millimeter, or in a range from 500 to 900micrometers, or in a range from 625 to 875 micrometers. This multi-filarcoil may have an inner diameter in a range from 100 to 1000 micromters,or from 250 to 800 micrometers, or from 250 to 600 micrometers. Theguide hub 200, 201 inner diameter may define an open lumen that may beconfigured to receive a stylet for lead placement.

FIG. 6 is a schematic diagram of an illustrative lead body filar coil121 having a variable pitch. The illustrative filar coil 121 is formedof eight lead filars 120. At an end proximal to the termination orconnection element is the loose coil portion 123. Distal from the loosecoil portion 123 is the tight coil portion 122. The tight coil portion122 may include filars forming a tight coil where adjacent filars toucheach other. The loose coil portion 123 may include filars forming aloose coil where adjacent filars do not touch each other and may bespaced apart from each other by a distance of at least 0.5 filardiameter or at least 1 filar diameter.

The loose coil portion 123 has a pitch P₂ that is greater than the tightcoil portion 122 pitch P₁. The loose coil portion 123 pitch P₂ may be atleast 1.5, 2, 2.5, or 3 times greater than the tight coil portion 122pitch P₁. As described above, each of the plurality of lead filars havea diameter of less than 150 micrometers, or less than 125 micrometers,or from 50 to 125 micrometers, or from 50 to 100 micrometers.

The lead body filar coil 121 may form a multi-filar coil having an outerdiameter of less than 1.5 millimeters or less than 1 millimeter or in arange from 500 to 900 micrometers, or in a range from 625 to 875micrometers. This multi-filar coil may have an inner diameter in a rangefrom 200 to 700 micromters, or from 350 to 550 micrometers. Themulti-filar coil inner diameter may define an open lumen that may beconfigured to receive a stylet for lead placement.

The lead body filar coil 121 has a longitudinal axis L_(A) that extendthrough the center of the coil length. The longitudinal axis L_(A)extends along the center of the filar coil and filars 120 forming thefirst pitch P₁ form a first acute angle relative to the longitudinalaxis L_(A) and filars forming the second pitch P₂ form a second acuteangle relative to the longitudinal axis L_(A) and the second acute angleis less than the first acute angle. In many embodiments, the first acuteangle is greater than 50 degrees or greater than 60 degrees or greaterthan 70 degrees and the second acute angle is less than 45 degrees orless than 40 degrees or less than 35 degrees.

Thus, embodiments of the MEDICAL DEVICE LEAD ASSEMBLY WITH VARIABLEPITCH COIL are disclosed. All references and publications cited hereinare expressly incorporated herein by reference in their entirety intothis disclosure, except to the extent they may directly contradict thisdisclosure. Although specific embodiments have been illustrated anddescribed herein, it will be appreciated by those of ordinary skill inthe art that a variety of alternate and/or equivalent implementationscan be substituted for the specific embodiments shown and describedwithout departing from the scope of the present disclosure. Thisapplication is intended to cover any adaptations or variations of thespecific embodiments discussed herein. Therefore, it is intended thatthis disclosure be limited only by the claims and the equivalentsthereof. The disclosed embodiments are presented for purposes ofillustration and not limitation.

1. A medical device lead assembly, comprising; an end connector elementcomprising a plurality of fixed connection element tabs eachrespectively extending from the end connector element to a tab distalend; a lead body comprising a plurality of lead filars extending throughthe lead body and forming a filar coil, each of the plurality of leadfilars coupled to a corresponding fixed connection tab, each of theplurality of lead filars have a diameter of less than 150 micrometers;the filar coil having an outer diameter value being less than 1.5 mm anda first pitch within the lead body and a second pitch adjacent to theend connector element and the second pitch is greater than the firstpitch.
 2. The assembly according to claim 1, wherein the second pitch isat least 1.5 times greater than the first pitch.
 3. The assemblyaccording to claim 1, wherein the second pitch is at least 2 timesgreater than the first pitch.
 4. The assembly according to claim 1,wherein plurality of filars comprise at least 8 filars.
 5. The assemblyaccording to claim 1, wherein a longitudinal axis extends along a centerof the filar coil and filars forming the first pitch form a first acuteangle relative to the longitudinal axis and filars forming the secondpitch form a second acute angle relative to the longitudinal axis andthe second acute angle is less than the first acute angle.
 6. Theassembly according to claim 5, wherein the first acute angle is greaterthan 50 degrees and the second acute angle is less than 45 degrees. 7.The assembly according to claim 1, further comprising a tubular guidehub extending from a hub proximal end to a hub distal end, the tubularguide hub comprising a plurality of guide elements circumferentiallydisposed about an outer surface of the guide hub, the hub distal enddisposed within the lead body and the hub proximal end received withinthe end connector element, and selected guide elements contact selectedlead filars forming the second pitch.
 8. The assembly according to claim7, wherein the plurality of guide elements comprises a plurality ofco-extending spiral channels and a selected lead filar of the pluralityof lead filars is disposed within a selected spiral channel.
 9. Theassembly according to claim 7, wherein the plurality of guide elementscomprises a plurality of posts extending away from the outer surface ofthe tubular guide element and the plurality of lead filars is disposedbetween the plurality of posts.
 10. The assembly according to claim 1,wherein each of the lead filars are formed of TiMo or a TiMo alloy. 11.The assembly according to claim 1, wherein the lead filars forming thesecond pitch are separated from adjacent lead filars by at least thediameter of the lead filer.
 12. A medical device article comprising; astimulator; a lead contact comprising at least one stimulationelectrode; a lead body providing stimulation signal communication to thestimulation electrode, the lead body comprising an end connectorassembly, the end connector assembly comprising: an end connectorelement comprising a plurality of fixed connection element tabsextending from the end connector element to a tab distal end; a leadbody comprising a plurality of lead filars extending through the leadbody and forming a filar coil, each of the plurality of lead filarscoupled to a corresponding fixed connection tab, each of the pluralityof lead filars have a diameter of less than 150 micrometers; the filarcoil having an outer diameter value being less than 1.5 mm and a firstpitch within the lead body and a second pitch adjacent to the endconnector element and the second pitch is greater than the first pitch.13. The medical device according to claim 12, wherein the second pitchis at least 2 times greater than the first pitch.
 14. The medical deviceaccording to claim 12, wherein the second pitch is at least 3 timesgreater than the first pitch.
 15. The medical device according to claim12, wherein plurality of filars comprise at least 8 filars.
 16. Themedical device according to claim 12, wherein a longitudinal axisextends along a center of the filar coil and filars forming the firstpitch form a first acute angle relative to the longitudinal axis andfilars forming the second pitch form a second acute angle relative tothe longitudinal axis and the second acute angle is less than the firstacute angle.
 17. The medical device according to claim 16, wherein thefirst acute angle is greater than 50 degrees and the second acute angleis less than 45 degrees.
 18. The medical device according to claim 12,further comprising a tubular guide hub extending from a hub proximal endto a hub distal end, the tubular guide hub comprising a plurality ofguide elements circumferentially disposed about an outer surface of theguide hub, the hub distal end disposed within the lead body and the hubproximal end received within end connector element, and selected guideelements contact selected lead filars forming the second pitch.